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In-situ pulsed laser induced growth of CdS nanoparticles on ZnO nanorods surfaces
摘要： Herein we present a process for the in-situ growth of CdS nanoparticles using a pulsed laser irradiation. A Nd-YAG laser was applied to ZnO nanorods previously submerged in an aqueous precursor solution containing cadmium chloride and thiourea. For optimum values of the laser fluence, around 40 mJ/cm2 it was possible to fabricate a highly homogeneous film of CdS nanoparticles covering the ZnO nanorods surface. Cathodoluminescence measurements of the ZnO/CdS structure show the quenching of the ZnO yellow and green luminescence, indicating the ZnO surface defects passivation by CdS nanostructures. Although lasers have been already used for inducing growth in solution, this work presents new evidence of in-situ growth on the surface of nanostructured materials. The laser based technique presented is simple, easy to implement, scalable and it could be applied in the fabrication of nanostructured solar cells and other devices.
关键词： A. Inorganic compounds,D. Defects,A. Nanostructures,B. Chemical synthesis,C. Electron microscopy
更新于2025-09-23 15:19:57
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Ge/Si Core/Shell Quantum Dots in an Alumina Matrix: Influence of the Annealing Temperature on the Optical Properties
摘要： Structures with Ge/Si nanoparticles (quantum dots) in an aluminum-oxide matrix are of interest due to the combination of two basic semiconductors and the use of a matrix with a high permittivity and strong oxygen–metal bonding. In this study, multilayer nanoperiodic structures in the form of a substrate/Al2O3/Ge/Si/Al2O3…Al2O3 sequence of layers (with the period Al2O3/Ge/Si and the number of periods up to 20) are produced and then annealed at different temperatures. It is shown that, after annealing, the structures contain both Ge and Si crystalline particles, whose dimensions and number are defined by the deposited-layer thicknesses and the annealing temperature. The results obtained by different optical techniques suggest that the structures exhibit the quantum-confinement effect. This inference is supported by high-resolution microscopy.
关键词： Ge/Si,multilayer nanostructures,core–shell quantum dots
更新于2025-09-23 15:19:57
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High-Efficiency Perovskite Solar Cells Enabled by Anatase TiO2 Nanopyramid Arrays with Oriented Electric Field
摘要： One-dimensional (1D) nanostructured oxides have been proposed as excellent electron transport materials (ETMs) for perovskite solar cells (PSCs), but this has not yet been demonstrated experimentally. Here, we exploit a facile hydrothermal approach to grow highly oriented anatase TiO2 nanopyramid arrays and further demonstrate their advantages for application in PSCs. The oriented TiO2 nanopyramid arrays afford sufficient contact area for electron extraction and increase light transmission. Moreover, the nanopyramid array/perovskite system exhibits an oriented electric field that can increase charge separation and accelerate charge transport, thereby suppressing charge recombination. As a result, the anatase TiO2 nanopyramid arrays-PSCs deliver a champion power conversion efficiency of ~22.5%, which is the highest PCE reported thus far for PSCs consisting of 1D ETMs. This work demonstrates that the rational design of 1D ETMs can achieve PSCs that perform as well as typical mesoscopic and planar PSCs.
关键词： Anatase TiO2,Electric field distribution,Perovskite solar cells,One-dimensional nanostructures,Nanopyramid arrays
更新于2025-09-23 15:19:57
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Lighta??Emitting Nanophotonic Designs Enabled by Ultrafast Laser Processing of Halide Perovskites
摘要： Nanophotonics based on resonant nanostructures and metasurfaces made of halide perovskites have become a prospective direction for efficient light manipulation at the subwavelength scale in advanced photonic designs. One of the main challenges in this field is the lack of large-scale low-cost technique for subwavelength perovskite structures fabrication preserving highly efficient luminescence. Here, unique properties of halide perovskites addressed to their extremely low thermal conductivity (lower than that of silica glass) and high defect tolerance to apply projection femtosecond laser lithography for nanofabrication with precise spatial control in all three dimensions preserving the material luminescence efficiency are employed. Namely, with CH3NH3PbI3 perovskite highly ordered nanoholes and nanostripes of width as small as 250 nm, metasurfaces with periods less than 400 nm, and nanowire lasers as thin as 500 nm, corresponding to the state-of-the-art in multistage expensive lithographical methods are created. Remarkable performance of the developed approach allows to demonstrate a number of advanced optical applications, including morphology-controlled photoluminescence yield, structural coloring, optical-information encryption, and lasing.
关键词： metasurfaces,structural coloration,lasing,halide perovskites,light emission,nanostructures
更新于2025-09-23 15:19:57
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[Institution of Engineering and Technology 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Lecce, Italy (23-25 May 2018)] 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Colloidal quantum dots for optoelectronic applications: fundamentals and recent progress
摘要： In this work, we present highlights and major milestones in the field of CQDs, starting from their optical and electronic properties that can be tailored not only by the atomic composition but also by the size, shape, and surface functionalization. We will also touch on CQD synthesis, processing and assembly, emphasizing their flexibility, low cost, low temperature and scalability. We will review recent advances in the design and fabrication of optoelectronic devices based on colloidal semiconductor quantum dots, with emphasis on light emitters, detectors and solar cells. We conclude with a short discussion on the large potentialities of this new class of materials as well as the challenges that must be addressed towards solution-processed functional optoelectronic nanomaterials for their practical applications in various fields.
关键词： semiconductor nanostructures,optoelectronic devices,colloidal quantum dots
更新于2025-09-23 15:19:57
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Enhancement of the second harmonic signal of nonlinear crystals by self-assembled gold nanoparticles
摘要： In second harmonic generation (SHG), the energy of two incoming photons, e.g., from a femtosecond laser, can be combined in one outgoing photon of twice the energy, e.g., by means of a nonlinear crystal. The SHG efficiency, however, is limited. In this work, the harvested signal is maximized by composing a hybrid system consisting of a nonlinear crystal with a dense coverage of plasmonic nanostructures separated by narrow gaps. The method of self-assembled diblock-copolymer-based micellar lithography with subsequent electroless deposition is employed to cover the whole surface of a lithium niobate (LiNbO3) crystal. The interaction of plasmonic nanostructures with light leads to a strong electric near-field in the adjacent crystal. This near-field is harnessed to enhance the near-surface SHG signal from the nonlinear crystal. At the plasmon resonance of the gold nanoparticles, a pronounced enhancement of about 60-fold SHG is observed compared to the bare crystal within the confocal volume of a laser spot.
关键词： gold nanoparticles,nonlinear crystal,second harmonic generation,lithium niobate,plasmonic nanostructures,electroless deposition,self-assembled diblock-copolymer-based micellar lithography,LiNbO3,SHG
更新于2025-09-23 15:19:57
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Light Emission from Selfa??Assembled and Lasera??Crystallized Chalcogenide Metasurface
摘要： Subwavelength periodic confinement can collectively and selectively enhance local light intensity and enable control over the photoinduced phase transformations at the nanometer scale. Standard nanofabrication process can result in geometrical and compositional inhomogeneities in optical phase change materials, especially chalcogenides, as those materials exhibit poor chemical and thermal stability. Here the self-assembled planar chalcogenide nanostructured array is demonstrated with resonance-enhanced light emission to create an all-dielectric optical metasurface, by taking advantage of the fluid properties associated with solution-processed films. A patterned silicon membrane serves as a template for shaping the chalcogenide metasurface structure. Solution-processed arsenic sulfide metasurface structures are self-assembled in the suspended 250 nm silicon membrane templates. The periodic nanostructure dramatically manifests the local light–matter interaction such as absorption of incident photons, Raman emission, and photoluminescence. Also, the thermal distribution is modified by the boundaries and thus the photothermal crystallization process, leading to the formation of anisotropic nanoemitters within the field enhancement area. This hybrid structure shows wavelength-selective anisotropic photoluminescence, which is a characteristic behavior of the collective response of the resonant-guided modes in a periodic nanostructure. The resonance-enhanced Purcell effect can manifest the quantum efficiency of localized light emission.
关键词： optical antennas,laser processing,optical nanostructures,metasurfaces,Raman emission
更新于2025-09-23 15:19:57
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MOVPE growth of n-GaN cap layer on GaInN/GaN multi-quantum shell LEDs
摘要： Embedded growth of an n-GaN cap layer on multi-quantum shells (MQSs) and nanowires through a tunnel junction (TJ) was investigated for the improvement of current injection to the m-plane of the MQSs. Different growth conditions for an n-GaN cap layer were systematically studied to suppress Mg diffusion and void formation, which are serious problems in this structure. At a high temperature of 900 °C and above, the growth rate on a semi-polar r-plane decreased, and large voids were formed at the bottom part of the nanowires owing to the diffusion of Ga atoms from the r-plane to the m-plane. When the growth temperature decreased to 800 °C, the growth rate on both the m-plane and the r-plane increased, and the size of voids decreased. Simultaneously, Mg diffusion also disappeared because of the low growth temperature of 800 °C. It was found that the growth with an extremely low V/III ratio of 20 at low temperatures increases the lateral growth rate on the m-plane, and void formation is fully suppressed when the MQS height is 700 nm or less.
关键词： B1. Nitrides,A1. Nanostructures,B3. Laser diodes,A3. Metalorganic vapor phase epitaxy
更新于2025-09-23 15:19:57
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Self-assembled line network in BiFeO3 thin films
摘要： In this work we report on the controlled fabrication of a self-assembled line network in highly epitaxial BiFeO3 thin films on top of LaAlO3 in the kinetically limited grown region by RF sputtering. As previously shown in the case of manganite thin films, the remarkable degree of ordering is achieved using vicinal substrates with well-defined step-terrace morphology. Nanostructured BiFeO3 thin films show mixed-phase morphology. Besides typical formation following (100) and (010) axes, some mixed phase nanodomains are detected also in-between the regular line network. These particular microstructures open a playground for future applications in multiferroic nanomaterials.
关键词： Mixed phase nanodomains,Long-range ordered nanostructures,Multiferroic thin films,Growth kinetic
更新于2025-09-23 15:19:57
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Controllable Patterning of Hybrid Silicon Nanowire and Nanohole Arrays by Laser Interference Lithography
摘要： Metal-assisted chemical etching (MACE) is a cost-effective method to fabricate Si nanostructures including silicon nanowires (SiNWs) and silicon nanoholes (SiNHs). However, the preparation of metallic template for MACE would require complex experimental conditions including strict cleaning process and multiple steps. In our study, we applied superlens-enhanced laser interference lithography to directly fabricate complicated metallic patterns and then used MACE to obtain hybrid SiNW and SiNH arrays. Ag films were firstly deposited on Si substrates, and then a 1064 nm high power laser source was utilized to generate two-beam interference electric fields. Since Ag molecules are very sensitive to any input energy change, they tend to break up or aggregate and form different Ag patterns which have a specific energy threshold in order to lower its free energy. By manipulating the distribution of input electric field, we are able to obtain complicated metallic patterns and their corresponding Si nanostructures with feature sizes that range from tens of nanometers to several micrometers.
关键词： silicon nanowires and silicon nanoholes,silicon nanostructures,nanofabrication,metal-assisted chemical etching
更新于2025-09-23 15:19:57